package com.duroty.controller.filters;

import java.io.IOException;
import java.util.Enumeration;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
 * Implementation of <code>javax.servlet.Filter</code> used to compress
 * the ServletResponse if it is bigger than a threshold.
 *
 * @author Amy Roh
 * @author Dmitri Valdin
 * @version $Revision: 1.3 $, $Date: 2006/07/20 12:38:16 $
 */
public class CompressionFilter implements Filter {
    /**
     * The filter configuration object we are associated with.  If this value
     * is null, this filter instance is not currently configured.
     */
    private FilterConfig config = null;

    /**
     * Minimal reasonable threshold
     */
    private int minThreshold = 128;

    /**
     * The threshold number to compress
     */
    protected int compressionThreshold;

    /**
     * Debug level for this filter
     */
    private int debug = 0;

    /**
     * Place this filter into service.
     *
     * @param filterConfig The filter configuration object
     */
    public void init(FilterConfig filterConfig) {
        config = filterConfig;

        if (filterConfig != null) {
            String value = filterConfig.getInitParameter("debug");

            if (value != null) {
                debug = Integer.parseInt(value);
            } else {
                debug = 0;
            }

            String str = filterConfig.getInitParameter("compressionThreshold");

            if (str != null) {
                compressionThreshold = Integer.parseInt(str);

                if ((compressionThreshold != 0) &&
                        (compressionThreshold < minThreshold)) {
                    if (debug > 0) {
                        System.out.println(
                            "compressionThreshold should be either 0 - no compression or >= " +
                            minThreshold);
                        System.out.println("compressionThreshold set to " +
                            minThreshold);
                    }

                    compressionThreshold = minThreshold;
                }
            } else {
                compressionThreshold = 0;
            }
        } else {
            compressionThreshold = 0;
        }
    }

    /**
    * Take this filter out of service.
    */
    public void destroy() {
        this.config = null;
    }

    /**
     * The <code>doFilter</code> method of the Filter is called by the container
     * each time a request/response pair is passed through the chain due
     * to a client request for a resource at the end of the chain.
     * The FilterChain passed into this method allows the Filter to pass on the
     * request and response to the next entity in the chain.<p>
     * This method first examines the request to check whether the client support
     * compression. <br>
     * It simply just pass the request and response if there is no support for
     * compression.<br>
     * If the compression support is available, it creates a
     * CompressionServletResponseWrapper object which compresses the content and
     * modifies the header if the content length is big enough.
     * It then invokes the next entity in the chain using the FilterChain object
     * (<code>chain.doFilter()</code>), <br>
     **/
    public void doFilter(ServletRequest request, ServletResponse response,
        FilterChain chain) throws IOException, ServletException {    	
        if (debug > 0) {
            System.out.println("@doFilter");
        }

        if (compressionThreshold == 0) {
            if (debug > 0) {
                System.out.println(
                    "doFilter gets called, but compressionTreshold is set to 0 - no compression");
            }

            chain.doFilter(request, response);

            return;
        }

        boolean supportCompression = false;

        if (request instanceof HttpServletRequest) {
            if (debug > 1) {
                System.out.println("requestURI = " +
                    ((HttpServletRequest) request).getRequestURI());
            }

            // Are we allowed to compress ?
            String s = (String) ((HttpServletRequest) request).getParameter(
                    "gzip");

            if ("false".equals(s)) {
                if (debug > 0) {
                    System.out.println(
                        "got parameter gzip=false --> don't compress, just chain filter");
                }

                chain.doFilter(request, response);

                return;
            }

            Enumeration e = ((HttpServletRequest) request).getHeaders(
                    "Accept-Encoding");

            while (e.hasMoreElements()) {
                String name = (String) e.nextElement();

                if (name.indexOf("gzip") != -1) {
                    if (debug > 0) {
                        System.out.println("supports compression");
                    }

                    supportCompression = true;
                } else {
                    if (debug > 0) {
                        System.out.println("no support for compresion");
                    }
                }
            }
        }

        if (!supportCompression) {
            if (debug > 0) {
                System.out.println("doFilter gets called wo compression");
            }

            chain.doFilter(request, response);

            return;
        } else {
            if (response instanceof HttpServletResponse) {            	            	
                CompressionServletResponseWrapper wrappedResponse = new CompressionServletResponseWrapper((HttpServletResponse) response);
                wrappedResponse.setDebugLevel(debug);
                wrappedResponse.setCompressionThreshold(compressionThreshold);

                if (debug > 0) {
                    System.out.println("doFilter gets called with compression");
                }

                try {
                	chain.doFilter(request, wrappedResponse);
                } finally {
                    wrappedResponse.finishResponse();
                }

                return;
            }
        }
    }

    /**
     * Set filter config
     * This function is equivalent to init. Required by Weblogic 6.1
     *
     * @param filterConfig The filter configuration object
     */
    public void setFilterConfig(FilterConfig filterConfig) {
        init(filterConfig);
    }

    /**
     * Return filter config
     * Required by Weblogic 6.1
     */
    public FilterConfig getFilterConfig() {
        return config;
    }
}
